CVE-2021-21347: XStream Arbitrary Code Execution Vulnerability
Summary
CVE-2021-21347: XStream is vulnerable to an Arbitrary Code Execution attack. Affects com.thoughtworks.xstream:xstream versions < 1.4.16. Fixed in 1.4.16. How to fix ↓
Also tracked for
- activemq · Bitnami
- libxstream-java · Debian:11
The same CVE-2021-21347 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
XStream is an open-source Java library that allows for the serialization and deserialization of Java objects to XML and back. It provides a simple API for converting Java objects to XML and vice versa. XStream is widely used in various applications and frameworks for data exchange and persistence. However, it is vulnerable to an Arbitrary Code Execution attack, which can allow a remote attacker to load and execute arbitrary code from a remote host by manipulating the processed input stream.
Vulnerability Detail
The vulnerability in XStream arises from a lack of proper input validation and filtering during the deserialization process. By crafting a malicious input stream, an attacker can exploit this vulnerability to execute arbitrary code on the target system. This can lead to various consequences, including remote code execution, data theft, and unauthorized access to sensitive information. It is important to note that users who have followed the recommendation to set up XStream's security framework with a whitelist limited to the minimal required types are not affected by this vulnerability.
How To Fix
Latest published version: 1.4.21 as of 22 Oct 2026
Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.4.16
This is the first release that contains the fix.
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Workaround
If updating to the latest version of XStream is not immediately feasible, there are workarounds available for different versions. These workarounds involve configuring XStream's security framework to mitigate the risk of the vulnerability. Detailed instructions for implementing the workarounds can be found in XStream's documentation for CVE-2021-21347.
Conclusion
The XStream Arbitrary Code Execution vulnerability (CVE-2021-21347) poses a significant risk to applications using XStream for XML serialization and deserialization. It is crucial to update to the latest version of XStream (1.4.16) or apply the recommended workarounds to protect against this vulnerability. Regularly monitoring for updates and following secure coding practices can help mitigate the risk of similar vulnerabilities in the future. For further support and assistance in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for com.thoughtworks.xstream:xstream →
FAQ
XStream is an open-source Java library that provides a simple API for converting Java objects to XML and vice versa. It is widely used for data exchange and persistence in various applications and frameworks.
The vulnerability allows a remote attacker to execute arbitrary code on the target system by manipulating the input stream. This can lead to remote code execution, data theft, and unauthorized access to sensitive information.
The vulnerability was discovered and reported by threedr3am.
To protect your application, it is recommended to update XStream to at least version 1.4.16. Additionally, you should follow the best practices for secure deserialization and implement proper input validation and filtering.
Yes, there are workarounds available for different versions of XStream. These workarounds involve configuring XStream's security framework to mitigate the risk of the vulnerability. Detailed instructions can be found in XStream's documentation for CVE-2021-21347.
Related vulnerabilities
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